Date of Graduation

5-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Magoulick, Daniel

Committee Member

DeGregorio, Brett

Second Committee Member

Lynch, Dustin

Third Committee Member

Willson, John David

Keywords

Darter; Drought; Endangered; Mesocosm; Snorkel; Underwater Camera

Abstract

Freshwater ecosystems are one of the most imperiled habitats across the world with biodiversity declining rapidly. There are many stressors contributing to freshwater species declines including habitat loss and degradation, land-use changes, anthropogenic water demands, changes in precipitation and weather extremes, and pollution. Current environmental projections predict that these stressors will continue to impact freshwater ecosystems to greater extents moving forward. Stream drying from drought conditions increasing in intensity and frequency is especially concerning in northern Arkansas where seasonal drought is typical in the summer and fall months. With increased drying conditions, the elimination of shallow-water riffle habitats in streams can pose life-threatening conditions. A particular species of concern in this region is the Yellowcheek Darter (Nothonotus moorei), which is an endangered, endemic, riffle-obligate species in the Little Red River, AR. Yellowcheek Darter populations have been declining for decades, largely due to habitat loss from the completion of Greers Ferry Dam, which isolated the species to the four headwater forks of the Little Red River. Due to the various threats affecting Yellowcheek Darters (i.e., ~80% population decline, limited habitat range, seasonal drought increases, and other anthropogenic factors) the species was listed as federally endangered in 2011. To effectively monitor and conserve endangered species, researchers need to evaluate populations regularly and utilize the knowledge gained to improve conservation plans. This involves evaluating how species respond to changing environments and how to best gain information with low risks to species. The studies included in this dissertation come together to gain insight into how Yellowcheek Darters and associated species respond to water loss in terms of behavioral refuge seeking ability, survival, and growth through laboratory mesocosm experiments. Additionally, this dissertation evaluates the utility of non-invasive snorkel and underwater camera survey methods to estimate density and detection probability while evaluating microhabitat use for Yellowcheek Darters and associated species in the Little Red River. The overall goal of these projects is to provide information to improve management of endangered freshwater species in riverine environments facing challenges of environmental and physical change.

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